Colorectal cancer (CRC) is a common malignancy, and remains the second leading cause of cancer-related deaths in the United States. The present guidelines for CRC treatment recommend that patients with stage III and IV colon cancers (with lymph node or distant metastasis) should be treated with adjuvant or palliative chemotherapy using cytotoxic drugs such as 5-fluorouracil (5-FU) and oxaliplatin after surgical resection of the primary cancer.In spite of our best intentions, a significant proportion of patients treated with chemotherapy derive no clinical benefit, though all are exposed to toxic and expensive therapeutic regimens. Therefore, there is a clear need to develop biomarkers that can help predict which subset of patients will or will not benefit from these treatment regimens. Currently there are no biomarkers available for determining response for oxaliplatin-based chemotherapy (FOLFOX) which serves as standard-of-care for treating patients with advanced CRC. The significance of the current proposal stems from the huge unmet clinical need for the lack of availability of a single established predictive/prognostic biomarker for stage III or IV CRC patients treated with oxaliplatin-based chemotherapy, which is the standard-of-care treatment for such patients. This gap in knowledge encouraged us to undertake systematic and comprehensive microRNA (miRNA) biomarker discovery using next generation sequencing approaches, rigorous biomarker prioritization and validation of candidate markers in multiple, independent patient cohorts, and potential translation of some of these aberrantly methylated genes/loci as blood-based, noninvasive biomarkers. To achieve these goals, we will pursue the following 3 specific aims: Aim #1: MiRNA biomarkers will be ?discovered? using miRNA-Seq in matched tumor and normal mucosa tissues from advanced CRC patients with and without response to FOLFOX chemotherapy. Aim #2: Candidate miRNA biomarkers will be ?clinically validated? and their ?performance evaluated? in primary tumor tissues from independent cohorts of stage III (adjuvant treatment) and stage IV (palliative treatment) CRC patients treated with FOLFOX. Aim #3: Determine the feasibility of translating ?tissue-based? miRNAs into ?plasma-based? predictive biomarkers in metastatic CRC patients treated with FOLFOX. This project will be undertaken by a team of investigators who have longstanding experience and track record in the field of cancer epigenetics and biomarker discovery. Our findings will have an important clinical impact in identifying patients who will benefit from current chemotherapeutic regimens, and those who are likely to experience adverse outcomes without benefit. The ability to identify such biomarkers will help reduce the overall healthcare cost burden associated with such treatments, and will provide a significant step forward into the era of personalized or precision medicine. 1